This invention relates to a composition for a sliding member having low friction properties and good wear resisting properties, and more specifically to a particular composition comprising fluorocarbon resin for use in forming, laminating, impregnating and coating sliding members or seal materials in part or in its entirety.
Hitherto, several synthetic resin compositions used for sliding members such as bearings or the like had been known, as well as sliding members made of such compositions. These are shown, for example, in (1) Japanese patent Examined Publication No. 31097/72, (2) Japanese patent Examined Publication No. 34698/77, (3) Japanese patent Unexamined Publication No. 166526/80, and (4) Japanese patent Unexamined Publication No. 103022/84.
First, the Publication (1) No. 31097/1972 discloses a composition having good lubricating property and wear resisting property and usable for bearings, the composition consisting of polytetrafluoroethylene formed as a continuous layer into which polyimide material is dispersed. Reference (2) Japanese Patent No. 34698/1972 discloses an oilless bearing containing polyfluoric addition polymer consisting of oxybenzoylpolyester and at least one unsaturated halogenated monomer selected from the group consisting of tetrafluoroethylene, perfluoropropylene, chlorotrifluoroethylene and vinylidene fluoride, at least 80 mol % of the hologen unit in the polymer being fluorine, the addition polymer being thermally stable at a temperature no less than 204.degree. C. (400.degree. F.), the polymer further containing oxybenzoylpolyester with the weight ratio of the former to the latter being 1:100 to 100:1.
Moreover, the reference (3) Japanese patent Unexamined Publication No. 166526/1980 discloses a sliding member and a manufacturing method thereof wherein the sliding surface of the member is coated with a 5-50 micron meter thick film of a synthetic resin consisting, by weight percent, of 90 to 97 wt% tetrafluoroethylene resin and 3 to 10 wt% polyphenylene sulfide resin. The reference (4) Japanese patent Laid-Open Publication No. 103022/1984 discloses a bearing material with good wear resisting property, wherein the material comprises a backing metal and a porous metal layer provided thereon on which layer is impregnated and coated any one of the following compositions: (A) a composition consisting of: a resin of the amount 0.1 to 50 volume % selected from the group consisting of tetrafluoroethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVDF), chlorotrifluoroethylene resin (PCTFE) and fluoroethylene propylene ether resin (EPE); and the balance substantially tetrafluoroethylene resin (PTFE), (B) a composition consisting of: at least one resin of the amount 0.1 to 50 volume % selected from the group consisting of tetrafluoroethylenehexafluoropropylene copolymer resin (FEP), tetrafluoro ethyleneperchloroalkylvinyl ether copolymer resin (PFA), ETFE, PVDF, PCTFE and EPE, and the balance substantially PTFE, and (c) a composition consisting of: at least one resin of the amount 0.1 to 50 volume % selected from the group consisting of FEP, PFA, ETFE, PVDF, PCTFE and EPE; at least one material of the amount 0.1 to 35 volume % selected from the group consisting of a lubricant of a metal with a low melting point such as lead, tin or their alloys, a solid lubricant such as metal oxide, metal sulfide, metal fluoride or graphite, a fibrous material such as carbon fiber, and a ceramic material such as silicon carbide; and the balance substantially of PTFE, the total amount of the constituents other than PTFE being 0.2 to 70 volume %.
Since these fluorine-based resin compositions or the sliding members comprising the compositions are excellent in their lubricating performance and their wear resisting properties, they have been widely used in the field in comparison with sliding members which comprise other resins.
As mentioned above, the materials disclosed in the references (1) through (4) are useful as the compositions for the sliding members. However, in view of the various properties which have been demanded for materials used in recent times, these compositions or the sliding members were not necessarily satisfactory, particularly in regard to the low friction property and the wear resisting property both of which are deemed to be very important to maintain a good sliding performance.